Mobile terminals—such as PDAs or smartphones—are often equipped with a WLAN interface to permit a wireless data exchange over it. Among other things, a WLAN (wireless local area network) allows a localization of the mobile terminal located within the network, thereby permitting site-based services such as navigation. The increasing coverage by WLAN networks in shopping arcades, at public places such as railway stations or airports and in companies is reinforcing the trend of such site-based services.